Attachment plug



F. B. ENNIS ATTACHMENT PLUG Nov. 3, 1931.

Filed April 3. 1930 mm P n w a M T L 101% s :M. F H m my Patented Nov. 3; 1931 FORD B. ENNIS, 01

PATENT OFFICE BBIDGEPORT. CONNECTICUT! '1, ASSIGNOR TO GENERAL ELECE'RIO comrm, A CORPORATION on NEW YORK ATTACEMEN '1 PLUG Application filed April 3, 1930. Serial No. 441,376.

tion'and cheap to manufacture. More spe cifically by reason of my improvements the use of metalinserts which have to be molded into the base is eliminated and at the same time the assembly of the parts is simplified. The use of such metal inserts is objectionable on account of the initial cost of the parts, loss due to defective parts in the molding operation, and to troubles incident to the inserts working loose when the plug is in service. i

A. further and very important feature of my improved construction resides in the fact that all of the contact parts of which there are four, are secured in their respective places on the insulating base by a single axially extending pin whlchis forced or driven into place and held therein by friction, and which also forms the center contact.

For a consideration of what Ibelieve to be novel and my invention, attention is-directed to the accompanying description and the claims appended thereto.

In the attached drawings, Fig. lis'a view in side elevation of an attachment plug; Fig. 2 is an axial section thereof; Fig. 3 is an exploded view of the parts of the lug; Fig. 4 1s a sectional view of a modi ed form of center contact; and Figs. 5 and 6 illustrate almodification of the cap at one end of the u 6 indicates the base or'insulating portion of the lug. It may be made of any suitable moldahle composition, of which there are many available on the market. The compo-;

sition may be molded either hot or cold depending upon-the characteristics thereof. It should be tough soas not to be easily broken, be slightly elastic and also have the necessary strength to withstand the ressures to which it is subjected in the assem ling operation.. On the lower end is a knurled flange 7 to facilitate screwing the plug into and out of the receiving part such asa'lamp socket or other receptacle. Rising above the flange 1s a cylindrical part which terminates ina shoulder 8 upon which the lower end of the thin metallic screw shell 9 is seated. Rising 5 above the shoulder is a central member 10 which has two flat parallel sides 11 which prevent the shell 9 from turning when the plug is screwed into place or when removed. (in each side of the member 10 are relatively ea deep recesses 12 which by their use decrease the amount of composition contained in the base and thereby efi'ect a small saving in material as well as in weight. In the member are two parallel openings 13 which for simplicity of assembly of the plug parts are made Identical. Each openin is of rectangular cross-section and extends entirely through the plug from top to bottom.

The shell 9 has a cylindrical portion which has the usual screw threads 15 for engagement with those in the cooperating socket or receptacle. It isalso provided with an integral top 16 which has two openings, one of which is much larger than the other. On opposite sides of the larger opening are two downwardly extending lips 17 which engage opposite sides of the central member 10 of the base toprevent the shell from turning independently thereof when screwed into or so unscrewed from the cooperating receptacle. This opening is also made large enough to prevent the contact member 18 where it rises above the member 10 from making electrical contact with the screw shell. The smaller opening 19 is arranged to receive that portion of the contact member 20 which .rises above the member 10. It is made of such size that the contact can pass freely through it and when so passed and properly positioned the inturned part 21 thereof will rest flatwise on the top of the screw shell and establish electrical contact therewith, and the lower part will be in one of the openings 13.

Referring now to the contactinember 18, it also is chiefly located in one of the-openings 13 in the base and has a relatively long inturned 'end or part 22\which connects with the center contact, to be referred to later.

The contact member extends through anarrow rectangular opening 23 in an element or disk 24 of insulating material which is seated firmly on the top of the screw shell. In the contact part 22, the disk 24 and the member 10 are aligned holes to receive the assembling pin 25 when the latter is seated. The pin has an enlarged smooth top head 26, a shank which presents a roughened peripheral surface 27 and a pilot 28. The roughening may be of any uitable form. I have found that fine screw t reads are satisfactory for the purpose and these may be formed in any suitable way, as for example, by a rolling operation. The transversely roughened surface of the pin, on its being driven or forced into place by axial pressure on the head cuts the insulating material of the base to a limited extent, which operation may bend the teeth or thread backward by a small amount. In any event the roughened surface grips the wall of the opening in the base so tightly that to pry it loose results in the practical destruction of the device as awhole. The kind of fit that the pin makes with the hole'29 in the insulating base is of course important. For a device of the size and character shown, the insulating member may be composed of a phenolic condensation product and a filler, the whole forming a nonfragile compound which when cured is slightly elastic, or in other words will yield slightly without cracking when the pin is forced into place. For a pin of the size of a 6/32 screw, the diameter of the hole 29 is made about .010 smaller than the outside diameter of the threads on the pin. The figures given are to be taken as illustrations and not as limitations of my invention, for it is evident that different compositions for the base and different roughen'ing of the pin or its diameter may require some modification as to sizes. The pilot 28 on the inner end of the pin serves to properly direct the pin through the various parts into the base during the assembly operation and has been found to be of material assistance. Where the pin is screw threaded it is advantageous to make the thread right handed so that when the device as a whole is screwed into a cooperating receptacle, any friction exerted on the head of the pin will tend to seat it more firmly.

It is desirable, on account of the construction of the socket or screw threaded. receptacle, to have the center contact elevated from the insulating disk 24. This may be done by a separable inverted cup 30 which may or may not be flanged at the bottom, as shown in Fig. 3, or the cup may be formed integral with the pin as shown in Fig. 4.

In Fig. 2 the plug is shown in axial section and the relation of the parts when assembled niay readily be observed. From this figure it will be seen that the lower ends of the contact members 18 and 20 are pressed outwardly into contact with the outer walls of the openings 13 in the base, are bent inwardly at about the middle section, and have buttonlike projections 32 which act as anchoring means for the blade of the attachment plug cap when mounted in place. I

After the screw shell, terminal members 18 and 20, and disk 24 are assembled in position, the pin 25 is mounted in place and by end-- wise pressure forced into the hole 29 by a iingle operation which completes the assem- It will be seen first that the base is molded wholly of insulating material and that no metal inserts of any character are required. Also, that all of the electrical parts, meaning thereby the screw shell 15, contact members l8 and 20, one of. which is in contact with the shell and the other with the center terminal or contact and the center terminal, are all fastened to the base by a single means, i. e., the pin 25 and that this is driven or forced by a single operation, as by a light hammer blow or press, into the base where it is securely held by a friction fit against movement. As a result of the simplification of parts, the cost of the parts of the device is reduced over prior constructions for the same purpose, as is also the assembly operation.

In Figs. 5 and 6 is illustrated a modified form of center contact. In this form of construction the insulating disk 24 is dispensed with and in place thereof is provided a cap or element 35 made of insulating material which may be the same as or different from that used in making the base 6. In this construction the contact member 18 is riveted to the cap. For this purpose the cap is provided with a rather deep rectangular recess 36 in its under side, and in which the end portion 22 of'the member is located and secured in place by the hollow rivet 37. By

making the boundary walls of the recess this case the head 26 of the pin 25 is somewhat larger than inthe previously described figures and is rounded so as to merge into the curved surface of the cap, thereby improving the appearance of the center contact end of the device. The fact that the head of the pin is seated on the upper flanged end of the hollow rivet insures good electrical connection between the pin and the member 18. The under side of the cap also engages the inturned end 21 of the contact 20 and holds the same in firm contact with'the top 16 of the screw shell 15.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. In an attachment plug, the combination of an insulating base which is slightly elastic and has a central fiat sided member conoewe? 'taining a pin receiving hole having a smooth has a slot through which the bent end of the second contact extends, and a pin having a transversely roughened body portion which makes a driving fit with the wall of said hole, is in electrical communication with the bent end of the second of said contacts, and also forms the center contact of the plug and unites said parts.

2. In an attachment plug, the combination of an insulating base containing a pin receiving hole having a smooth wall and also a pair of axially extending openings, a pair of contact members located one in each of said openings,,b0th of which members have inturned ends, a screw shell which is mounted on and surrounds a part of the base and is in electrical contact with one of said members, downturned lips on the shell which engage the base to prevent-the shell from turning thereon, an insulating element which covers one end of the shell and insulates the sec ond contact member from said shell, and a center contact with which the second contact member is in electrical communication, said contact comprising a. pin which makes a drivin g fit with the wall of the hole and unites the said parts and an inverted cup which is integral with the pin and is situated between its head and the insulating element.

3. In an attachment plug, the combination of an insulating base which is slightly elastic and has a flat sided member, said member having a smooth walled pin receiving hole and also a pair of axially extending through openings, a screw shell mounted on the base and having a pair of openings of differing sizes in the top thereof, the larger of which has lips that engage the sides of the member to prevent the shell from turning independcntly thereof, a pair of contact members located within the through openings, one of said members projecting through the smaller of said openings in the shell and having a bent end that engages the top of the shell, an insulating element which covers the top of the shell and has a slot to receive the bent end of the second contact and also insulates the contact from the screw shell and first mentioned contact, and a pin which makes a driving fit withthe wall of the hole in said member to unite the parts, is in electrical communication with the second contact mombelgr and also forms the center contact of the p ug. i

In witness whereof, I have hereunto set my hand this first day of April, 1930. I

\ FORD B. ENNIS. 

